The present invention relates to an apparatus for circulating a blowby gas within a crankcase of an internal combustion engine to an intake system via a valve chamber within a cylinder head, and, specifically, to an improved blowby gas circulating apparatus for delivering the blowby gas from the valve chamber into engine cylinders.
Japanese Utility Model Application First Publication No. 5-30412 discloses a blowby gas circulating apparatus for an internal combustion engine, in which a blowby gas path is formed in a flange of an intake manifold mounted to a side surface of a cylinder head. A blowby gas flowing from the cylinder head is delivered into the blowby gas path via a hose and then distributed into four engine cylinders. The blowby gas path is provided in the form of a recess formed on an end surface of the intake manifold flange which abuts on the side surface of the cylinder head. The blowby gas path has a so-called tournament structure. The blowby gas path includes an inlet, two upstream passages branched from the inlet in a fore-and-aft direction along a row of the four engine cylinders, and two downstream passages branched from each of the two upstream passages in the fore-and-aft direction.